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Abstract:

A coupler circuit that includes two parallel coupled transmission lines
(first transmission line and second transmission line) and a third
transmission line, one end of the third transmission line connects to the
end of first transmission line at one side, the other end of the third
transmission line connects to the end of the second transmission line at
the other side. Various coupling value and impedance transforming ratio
can be achieved by select corresponding even and odd mode impedance of
the coupled transmission lines and characteristic impedance of the
crossing transmission line.

Claims:

1. A coupler circuit that operates at at least a nominal operating
frequency, the coupler circuit comprising: a first port rated at a first
impedance; a second port rated at a first impedance; a third port rated
at a second impedance; a fourth port rated at the second impedance; a
pair of coupled lines, comprising a first coupled line and a second
coupled line; and crossing line circuitry having a crossing line
impedance; wherein: the first coupled line has a first end and a second
end; the second coupled line has a first end and a second end; the
crossing line circuitry has a first terminal and a second terminal; the
first and second coupled lines have a geometry and spacing so that, at
the nominal operating frequency, the first and second lines act as
coupled line pair having an odd mode impedance and an even mode
impedance; the first port is electrically connected to: (i) the first end
of the first coupled line, and (ii) the first terminal of the crossing
line circuitry; the second port is electrically connected to: (i) the
second end of the second coupled line, and (ii) the second terminal of
the crossing line circuitry; the third port is electrically connected to
the first end of the second coupled line; the fourth port is electrically
connected to the second end of the first coupled line; and the odd mode
impedance, the even mode impedance and the crossing line impedance are
selected so that the coupler circuit transforms electrical signals, at
the nominal operating frequency, between: (i) the first impedance, at the
first and/or second ports, and (ii) the second impedance, at the third
and/or fourth ports.

2. A coupler circuit that operates at at least a nominal operating
frequency, the coupler circuit comprising: a first port rated at a first
impedance; a second port rated at a first impedance; a third port rated
at a second impedance; a fourth port rated at the second impedance; a
pair of coupled strip lines, comprising a first coupled strip line and a
second coupled line; crossing line circuitry including a strip
transmission line and having a crossing line impedance; a dielectric
substrate; wherein: the first coupled strip line has a first end and a
second end; the second coupled strip line has a first end and a second
end; the crossing line circuitry has a first terminal and a second
terminal; the first and second coupled strip lines have a geometry and
spacing so that, at the nominal operating frequency, the first and second
strip lines act as coupled line pair having an odd mode impedance and an
even mode impedance; the first port is electrically connected to: (i) the
first end of the first coupled strip line, and (ii) the first terminal of
the crossing line circuitry; the second port is electrically connected
to: (i) the second end of the second strip coupled line, and (ii) the
second terminal of the crossing line circuitry; the third port is
electrically connected to the first end of the second coupled strip line;
the fourth port is electrically connected to the second end of the first
coupled strip line; the odd mode impedance, the even mode impedance and
the crossing line impedance are selected so that the coupler circuit
transforms electrical signals, at the nominal operating frequency,
between: (i) the first impedance, at the first and/or second ports, and
(ii) the second impedance, at the third and/or fourth ports; and the
first and second coupled strip lines and the strip transmission lines are
printed on the substrate.

3. A coupler circuit that operates at at least a nominal operating
frequency and nominal operating wavelength, the coupler circuit
comprising: a first port rated at a high impedance; a second port rated
at a high impedance; a third port rated at a low impedance; a fourth port
rated at the low impedance; a pair of coupled lines, comprising a first
coupled line and a second coupled line; and crossing line circuitry
comprising a first terminal, a strip transmission line and a second
terminal; wherein: the crossing line circuitry has a crossing line
impedance; the strip transmission line is one quarter wavelength in
length; the first coupled line has a first end and a second end; the
second coupled line has a first end and a second end; the first and
second coupled lines have a geometry and spacing so that, at the nominal
operating frequency, the first and second lines act as coupled line pair
having an odd mode impedance and an even mode impedance; the first port
is electrically connected to: (i) the first end of the first coupled
line, and (ii) the first terminal of the crossing line circuitry; the
second port is electrically connected to: (i) the second end of the
second coupled line, and (ii) the second terminal of the crossing line
circuitry; the third port is electrically connected to the first end of
the second coupled line; the fourth port is electrically connected to the
second end of the first coupled line; and the odd mode impedance, the
even mode impedance and the crossing line impedance are selected so that
the coupler circuit transforms electrical signals, at the nominal
operating frequency, between: (i) the high impedance, at the first and/or
second ports, and (ii) the low impedance, at the third and/or fourth
ports.

4. The circuit of claim 3 further comprises a first dielectric substrate,
wherein the pair of coupled lines and the crossing line circuitry are
printed on the first dielectric substrate.

5. The circuit of claim 4 wherein: the dielectric substrate has two,
opposing major surfaces; and each coupled line of the pair of coupled
lines is respectively printed on an opposite major surfaces of the first
dielectric substrate.

6. The circuit of claim 5 wherein the crossing line circuitry is
partially printed on each of the two, opposing major surfaces of the
first dielectric substrate.

Description:

CROSS REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority to applicant's U.S.
Provisional Application Ser. No. 61/381,769, filed on Sep. 10, 2010, the
entirety of which is incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates generally Microwave/RF transmission
hardware and more specifically to a coupler that transforms impedance as
between its first side port(s) and second side port(s).

[0004] 2. Description of the Related Art

[0005] A 90 degree 3 decibel (dB) hybrid coupler is a passive four-port
device. A coupler has four ports: input, transmitted, coupled, and
isolated. In a signal-dividing operation, the coupler divides an incident
signal (for example, radio frequency (RF) signal or microwave frequency
signal) at the input port into two signals paths, one output at the
transmitted port and the other output at the coupled port. The signals at
the transmitted port and at the coupled port are of equal amplitude and
have a relative 90 degree phase difference. As a reciprocal device, the
coupler can also combine two signals that are 90 degrees apart in phase.
In a combining operation transmitted port and coupled port output that
combined signal at the input port. The splitting and recombining
properties make the hybrid couplers useful in a wide range of RF
circuits, such as low noise amplifier, power amplifier, attenuator,
mixers and so on.

[0006] Typically, all four ports of the coupler have the same port
impedance which is matched to whatever standard RF system impedance is
being used in a given system (usually 50 ohms or 75 ohms). The impedance
of the circuits in the previous stage and the next stage also need to
match to the system impedance, in order to maximize the power transfer
through the coupler. For example, in power amplifier design, output
matching circuit is essential to transform a typical low impedance of the
transistor to the system impedance (usually, 50 ohms or 75 ohms). The
impedance transformation is conventionally realized by electrically
connecting at least one set of ports of the coupler to extraneous circuit
elements. These extraneous circuit elements used to match impedance may
be: (i) lumped elements, such as inductors and capacitors, and/or (ii)
distributed elements, such as quarter-wavelength transmission lines. As a
couple of preliminary notes on terminology: (i) any type of current
carrier that acts as a transmission line will generally be herein
referred to as a "transmission line; and (ii) a transmission line that
has the form of a strip of conductive material will herein generally be
called a "strip line" or a "strip transmission line; and (ii) for the
most part these terms will be used interchangeably herein, even though
they denote a genus (that is, transmission lines) and a species (that is,
transmission strip lines). There are inevitably limitations on bandwidth,
insertion loss, layout area and cost associated with these extraneous
output matching circuits. Generally speaking, the higher the impedance
transform ratio that is required, the more performance of the coupler
circuitry is degraded.

[0007] The difficulty of these matching circuits can be alleviated, if the
coupler is structured to have an impedance transforming function. Instead
of directly matching to system impedance, a transforming coupler can
transform the system impedance into an intermediate impedance first. The
matching circuit of the previous or next stage then matches to this
intermediate impedance instead of to the system impedance. Choosing the
proper intermediate impedance can lower the required impedance transform
ratio. This results in the design simplification and/or performance
improvement of the matching circuits, as well as size and cost reduction.

[0008] As an example of a conventional couple having an impedance
transforming function, patent application Publication No: US 2009/0295497
("497 Dowling") discloses an impedance transforming hybrid coupler that
is realized by cascading two impedance transforming circuits in series
with output ports of a conventional hybrid coupler, and integrating these
separated function blocks into same package, as shown in 497 Dowling at
its FIG. 1. The drawbacks of this solution are increased insertion loss
and increased circuit size due to the inserted impedance transforming in
the couplers of 497 Dowling.

[0010] Description Of the Related Art Section Disclaimer: To the extent
that specific publications are discussed above in this Description of the
Related Art Section, these discussions should not be taken as an
admission that the discussed publications (for example, published
patents) are prior art for patent law purposes. For example, some or all
of the discussed publications may not be sufficiently early in time, may
not reflect subject matter developed early enough in time and/or may not
be sufficiently enabling so as to amount to prior art for patent law
purposes. To the extent that specific publications are discussed above in
this Description of the Related Art Section, they are all hereby
incorporated by reference into this document in their respective
entirety(ies).

BRIEF SUMMARY OF THE INVENTION

[0011] At least some embodiments of the present invention are directed to
a four port coupler where the two ports a of port pair (that is, the
input/isolated port pair or the transmitted/coupled port pair) are
electrically connected to each other with a crossing line. This crossing
line does not necessarily directly mechanically connect to the ports, and
will often be connected to current paths, within the four port coupler,
that respectively lead to the ports of the connected port pair. While it
may be possible to make a crossing line of the present invention using
lines with lumped elements inserted into it, this is not necessarily
preferred. Rather, in preferred embodiments, the crossing line will be a
conduction path with a strip line inserted into it. If the transmission
line is on the high impedance side, then it should preferably be
(λ/4)+nλ in length, where n is an odd integer (preferably 0)
and λ is the operational wavelength of the coupler. If the strip
line is on the low impedance side, then it should preferably be
(3λ/4)+nλ in length, where n is an integer (preferably 0) and
λ is the operational wavelength of the coupler. In preferred
embodiments of the present invention, the following characteristics of
the coupler circuit are deigned to accomplish a relatively efficient
impedance transformation: (i) odd mode impedance of the coupled lines of
the coupler; (ii) even mode impedance of the coupled lines of the
coupler; and (iii) impedance of the crossing line.

[0012] Some aspects of the present invention relate to a novel coupling
structure with an intrinsic impedance transforming property. The
impedance transforming property is characterized as "intrinsic" because
it is accomplished by circuitry (for example, a crossing line with an
inserted strip line) that is electrically connected within the four ports
of the four port coupler. In other words, no extraneous circuitry must be
connected outside of the four ports, such as the extraneous impedance
transforming stage of 497 Dowling. The actual impedance adjusting means
is inherently parallel to the overall structure and hence even reduces
the insertion loss. At least some embodiments of the present invention
are advantageous with respect to over insertion loss performance and
reduced size.

[0013] According to one aspect of the present invention, a coupler circuit
operates at at least a nominal operating frequency. The coupler circuit
includes: a first port rated at a first impedance; a second port rated at
a first impedance; a third port rated at a second impedance; a fourth
port rated at the second impedance; a pair of coupled lines (including a
first coupled line and a second coupled line); and crossing line
circuitry (having a crossing line impedance). The first coupled line has
a first end and a second end. The second coupled line has a first end and
a second end. The crossing line circuitry has a first terminal and a
second terminal. The first and second coupled lines have a geometry and
spacing so that, at the nominal operating frequency, the first and second
lines act as coupled line pair having an odd mode impedance and an even
mode impedance. The first port is electrically connected to: (i) the
first end of the first coupled line, and (ii) the first terminal of the
crossing line circuitry. The second port is electrically connected to:
(i) the second end of the second coupled line, and (ii) the second
terminal of the crossing line circuitry. The third port is electrically
connected to the first end of the second coupled line. The fourth port is
electrically connected to the second end of the first coupled line. The
odd mode impedance, the even mode impedance and the crossing line
impedance are selected so that the coupler circuit transforms electrical
signals, at the nominal operating frequency, between: (i) the first
impedance, at the first and/or second ports, and (ii) the second
impedance, at the third and/or fourth ports.

[0014] According to a further aspect of the present invention, a coupler
circuit operates at at least a nominal operating frequency. The coupler
circuit includes: a first port rated at a first impedance; a second port
rated at a first impedance; a third port rated at a second impedance; a
fourth port rated at the second impedance; a pair of coupled strip lines
(including a first coupled strip line and a second coupled line);
crossing line circuitry (including a strip transmission line and having a
crossing line impedance; and a dielectric substrate. The first coupled
strip line has a first end and a second end. The second coupled strip
line has a first end and a second end. The crossing line circuitry has a
first terminal and a second terminal. The first and second coupled strip
lines have a geometry and spacing so that, at the nominal operating
frequency, the first and second strip lines act as coupled line pair
having an odd mode impedance and an even mode impedance. The first port
is electrically connected to: (i) the first end of the first coupled
strip line, and (ii) the first terminal of the crossing line circuitry.
The second port is electrically connected to: (i) the second end of the
second strip coupled line, and (ii) the second terminal of the crossing
line circuitry. The third port is electrically connected to the first end
of the second coupled strip line. The fourth port is electrically
connected to the second end of the first coupled strip line. The odd mode
impedance, the even mode impedance and the crossing line impedance are
selected so that the coupler circuit transforms electrical signals, at
the nominal operating frequency, between: (i) the first impedance, at the
first and/or second ports, and (ii) the second impedance, at the third
and/or fourth ports. The first and second coupled strip lines and the
strip transmission lines are printed on the substrate.

[0015] According to a further aspect of the present invention, a coupler
circuit operates at at least a nominal operating frequency and nominal
operating wavelength. The coupler circuit includes: a first port rated at
a high impedance; a second port rated at a high impedance; a third port
rated at a low impedance; a fourth port rated at the low impedance; a
pair of coupled lines (including a first coupled line and a second
coupled line); and crossing line circuitry (including a first terminal, a
strip transmission line and a second terminal). The crossing line
circuitry has a crossing line impedance. The strip transmission line is
one quarter wavelength in length. The first coupled line has a first end
and a second end. The second coupled line has a first end and a second
end. The first and second coupled lines have a geometry and spacing so
that, at the nominal operating frequency, the first and second lines act
as coupled line pair having an odd mode impedance and an even mode
impedance. The first port is electrically connected to: (i) the first end
of the first coupled line, and (ii) the first terminal of the crossing
line circuitry. The second port is electrically connected to: (i) the
second end of the second coupled line, and (ii) the second terminal of
the crossing line circuitry. The third port is electrically connected to
the first end of the second coupled line. The fourth port is electrically
connected to the second end of the first coupled line. The odd mode
impedance, the even mode impedance and the crossing line impedance are
selected so that the coupler circuit transforms electrical signals, at
the nominal operating frequency, between: (i) the high impedance, at the
first and/or second ports, and (ii) the low impedance, at the third
and/or fourth ports.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be more fully understood and appreciated
by reading the following Detailed Description in conjunction with the
accompanying drawings, in which:

[0017]FIG. 1A is a schematic view of a first embodiment of a coupler
according to the present invention;

[0018]FIG. 1B is a schematic view of a second embodiment of a coupler
according to the present invention;

[0019] FIG. 2 is a schematic view of a third embodiment of a coupler
according to the present invention;

[0020]FIG. 3 is a graph showing certain performance characteristics of
the third embodiment coupler;

[0021] FIG. 4 is a schematic view of a fourth embodiment of a coupler
according to the present invention;

[0023]FIG. 6 is a schematic view of a power amplifier combining circuit
using a prior art coupler;

[0024]FIG. 7 is a schematic view of a first embodiment of a power
amplifier circuit according to the present invention;

[0025] FIG. 8 is a plan view of a fifth embodiment of a coupler circuit
according to the present invention;

[0026]FIG. 9 is a cross-sectional view of a portion of the fifth
embodiment coupler circuit (cross-hatching omitted for clarity of
illustration purposes);

[0027]FIG. 10 is a plan view of a fourth metal layer of the fifth
embodiment coupler;

[0028]FIG. 11 is a plan view of a first metal layer of the fifth
embodiment coupler;

[0029]FIG. 12 is a plan view of a second metal layer of the fifth
embodiment coupler;

[0030]FIG. 13 is a plan view of a first via set of the fifth embodiment
coupler;

[0031]FIG. 14 is a plan view of a second metal layer of the fifth
embodiment coupler;

[0032] FIG. 15 is a plan view of a second via set of the fifth embodiment
coupler;

[0033]FIG. 16 is a schematic view of a second embodiment of a power
amplifier circuit according to the present invention; and

[0034]FIG. 17 is a schematic view of a third embodiment of a power
amplifier circuit according to the present invention;.

DETAILED DESCRIPTION OF THE INVENTION

[0035] As shown in FIG. 1A, coupler circuit 100 includes: high impedance
side port pair 102 (including first high impedance side port 102a and
second high impedance side port 102b); first coupled line 104; second
coupled line 105; low impedance side port pair 108 (including first low
impedance side port 108a and second low impedance side port 108b); and
crossing line 112 (including high impedance side circuit elements 114).
By connecting crossing line 112, with its high impedance side circuit
elements 114) across the pair of high impedance ports, coupler 100 will
have a high impedance at its high impedance port pair 102, while
maintaining a relatively lower impedance at its low impedance port pair
108. The high impedance side circuit elements are chosen so that the
impedance will be transformed between high and low when the coupler
operates in a coupling mode and/or in a splitting mode.

[0036] Some specific examples of high impedance side circuit element(s)
will be discussed below in connection with other embodiments. However, it
is noted that the present invention is not necessarily limited to the
preferred, specific high impedance side circuit element(s) specifically
discussed below. The specific high impedance side circuit element(s) may
include lumped circuit element(s) and/or distributed circuit element(s).

[0037] As shown in FIG. 1B, coupler circuit 150 includes: high impedance
side port pair 152 (including first high impedance side port 152a and
second high impedance side port 152b); first coupled line 154; second
coupled line 155; low impedance side port pair 158 (including first low
impedance side port 158a and second low impedance side port 158b); and
crossing line 162 (including low impedance side circuit elements 164). By
connecting crossing line 162, with its low impedance side circuit
elements 164) across the pair of low impedance ports, coupler 150 will
have a high impedance at its high impedance port pair 102, while
maintaining a relatively lower impedance at its low impedance port pair
108. The low impedance side circuit elements are chosen so that the
impedance will be transformed between high and low when the coupler
operates in a coupling mode and/or in a splitting mode.

[0038] As shown in FIG. 2, coupler 200 includes: first high impedance port
204; second high impedance port 208; first low impedance port 210; second
low impedance port 212; coupled strip lines 206; and strip transmission
line 202. In this example: (i) port 204 is rated at 50 ohms (zs); (ii)
port 208 is rated at 50 ohms (zs); (iii) port 210 is rated at 25 ohms
(zl); (iv) port 212 is rated at 25 ohms (zl); (v) the nominal operating
frequency/wavelength of coupler 200 is in the radio frequency (RF) or
microwave range; (vi) coupled strip lines 206 are formed as strip lines
on a printed circuit board (PCB) substrate; (vii) coupled strip lines 206
are designed to have an even mode impedance (Ze) of 50,000 ohms; (ix)
coupled strip lines 206 are designed to have an odd mode impedance (Zo)
of 12.5 ohms; (x) transmission line 202 has an impedance (Zt) of 50 ohms;
and (xi) transmission line 202 is one quarter wavelength of the nominal
operating wavelength.

[0039] In the design of coupler 200, the crossing line is connected
between the high impedance ports and the length of its transmission line
is one quarter wavelength. Alternatively (or additionally), a crossing
line could be placed across the low impedance ports. In this case the
length of the strip transmission line between the low impedance terminals
would be three-quarter wavelength.

[0040] In coupler 200, the impedance is transformed, by operation of the
circuit, because of selection of the following parameters: (i) impedance
of strip transmission line 202; (ii) even mode impedance (Ze) of coupled
lines 206; and (ii) odd mode impedance (Zo) of coupled lines 206. As will
be appreciated by those of skill in the art, these impedance parameters
may be designed and controlled by controlling: (i) the dimensions of the
strip lines; (ii) the spacing and/or dielectric between and around the
coupled lines; and/or (iii) the relative spatial orientation of the
coupled strip lines (for example, directly facing each other or partially
offset). As will be seen by comparing coupler 200 with coupler 300, there
is no exact formula for calculating transmission line impedance and
couple mode impedances that will work in an operative,
impedance-transforming coupler circuit. However, those of skill in the
art will be able to determine and fine tune these impedance values,
dependent upon specific application requirements.

[0041] As shown in FIG. 3, graph 201 shows some of the performance
characteristics for coupler 200, based on the impedance values as set
forth above.

[0042] As shown in FIG. 4, coupler 300 includes: first high impedance port
304; second high impedance port 308; first low impedance port 310; second
low impedance port 312; coupled strip lines 306; and strip transmission
line 302. In this example: (i) port 304 is rated at 50 ohms (zs); (ii)
port 308 is rated at 50 ohms (zs); (iii) port 310 is rated at 25 ohms
(zl); (iv) port 312 is rated at 25 ohms (zl); (iv) coupled strip lines
306 are designed to have an even mode impedance (Ze) of 275 ohms; (v)
coupled strip lines 306 are designed to have an odd mode impedance (Zo)
of 13 ohms; and (vi) transmission line 302 has an impedance (Zt) of 70
ohms.

[0043] As shown in FIG. 5, graph 301 shows some of the performance
characteristics for coupler 300, based on the impedance values as set
forth above. Note how performance has changed, relative to performance of
coupler 200 shown in graph 201, because of the changes made to the
characteristics of the coupled lines and the strip transmission line.

[0044] The coupled transmission lines (206 in coupler 200 and 306 in
coupler 300) are of a quarter-wavelength long at center frequency and
have the even and odd mode impedance of Ze and Zo. The third transmission
line (line 202 in coupler 200 and line 302 in coupler 300) is also a
quarter-wavelength long at center frequency and has the characteristic
impedance of Zt. With transmission lines connected in described
configuration, an impedance transforming coupler can be realized.

[0045] The design equations for 3 dB coupler with impedance transforming
from Zs (port impedance of the high impedance port pair 204/208 and
304/308) to Zl (Port impedance port impedance of the low impedance port
pair 210/212 and 310/312) are:

Zt=Zs/((Zs/Zl)-1);

[0046] Characteristic impedance of the coupled transmission lines:

Zc=(1/Zs 2-1/Zt 2) 0.5

[0047] Coupling value of the coupled transmission lines:

c=(h 2/(1+h 2)) 0.5, where h=Zc/Zl

[0048] From Zc and c, the even and odd mode impedance of the coupled
transmission lines are determined by the following equations:

Ze=(Zc 2*r) 0.5

Zo=(Zc 2/r) 0.5; where r=(1+c)/(1-c).

[0049] The impedance transforming range for this structure is:

2>Zs/Zl>1.

[0050] Design tradeoff between bandwidth and level of matching can be made
by varying the Ze, Zo and Zt. FIGS. 4 and 5 show such a schematic
variation and its resulting RF performance.

[0051] Various coupling value and impedance transforming ratio can be
achieved by selecting corresponding Ze, Zo and Zt.

[0053] As shown in FIGS. 6 and 7, in a balanced power amplifier
architecture, by taking part of the matching circuit inside the coupler,
reducing the required impedance transform ratio in power amplifiers'
output matching circuits, lower insertion loss can be achieved with the
size and cost reduction.

[0054] 3 dB is merely one example of a coupling value that may be used in
circuitry according to the present invention. Exact design equation for
coupling values that are not 3 dB may or may not exist. However, even if
the exact ideal solution of the other coupling value in the structure
does not exist, it would still be possible to do realistic designs by
using compromise techniques as is known in the art of RF and microwave
circuit design.

[0056] However, because couplers according to the present invention can
transform Zs to Zl from the high impedance port pair 204/208, 304/308 to
the low impedance port pair 210/212, 310/312, it can also transform Zl to
Zs from the low impedance port pair to the high impedance port pair, at
least in preferred embodiments of the present invention that are
structured to have the reciprocal property mentioned above. In other
words, if the structure is rotated 180 degrees, the realizable impedance
transform ratio becomes: 1>Zs/Zl>0.5.

[0057] Coupler 600 will now be discussed with reference to FIGS. 8 to 15.
Coupler 600 is formed by printed circuit board techniques, using
conventional printed circuit board lines, vias, ports, dielectric
substrate boards, etc. As best shown in the partial cross-sectional view
of FIG. 9, coupler 600 includes: second via set 602; fourth metal layer
604; third dielectric layer 606; first via set 608; third metal layer
610; second dielectric layer 612; second metal layer 614; first
dielectric layer 616; and first metal layer 618; 50 ohm port pair 650; 25
ohm port pair 652; crossing line (including segments 654a, 654b, 654c);
and coupled lines 656. FIG. 8 shows a plan view of the metal and via
layers. FIGS. 10 to 15 respectively isolate each metal and via layer so
that those of skill in the art will understand how embodiment 600 is
constructed.

[0058] As shown in FIGS. 12 and 14, the coupled lines are at the second
and third metal layers (with the second dielectric layer interposed
between the coupled lines). As shown in FIGS. 12, 13 and 14, the crossing
transmission line is split between the second metal layer, the third
metal layer and the first via set. As best shown in FIG. 15, the second
via set: (i) joins the ground plane portion first and fourth metal layers
together by vias 602a; and (ii) joins the first metal layer ports to the
second and third metal layer coupler circuitry by vias 602b.

[0059] As shown in FIG. 16, one application for couplers according to the
present invention is in a balanced power amplifier circuit 700. Circuit
700 includes: splitter 704; first 25 ohm amplifier 706; second 25 ohm
amplifier 708; and impedance transforming coupler 200. In circuit 700,
impedance transforming coupler 200 is used as a combiner, which means
that the amplifiers can be matched at 25 ohms, instead of the
conventional 50 ohms. This makes it easier to design amplifier output
matching. Also, the matching network will generally have less insertion
loss and wider bandwidth.

[0060] As shown in FIG. 17, another application for couplers according to
the present invention is in a balanced dual Doherty power amplifier
circuit 800. Circuit 800 includes: first splitter 804; second splitter
806; third splitter 812; first main amp 814; first peak amp 816; second
peak amp 818; second main amp 820; quarter wavelength transmission strip
lines 822 and 824; and impedance transforming coupler 200. This design
has two fewer quarter wavelength strip lines, as compared to similar
conventional balanced Doherty circuits, which saves space and decreases
insertion loss.

DEFINITIONS

[0061] Any and all published documents mentioned herein shall be
considered to be incorporated by reference, in their respective
entireties, herein to the fullest extent of the patent law. The following
definitions are provided for claim construction purposes:

[0062] Present invention: means at least some embodiments of the present
invention; references to various feature(s) of the "present invention"
throughout this document do not mean that all claimed embodiments or
methods include the referenced feature(s).

[0063] Embodiment: a machine, manufacture, system, method, process and/or
composition that may (not must) meet the embodiment of a present, past or
future patent claim based on this patent document; for example, an
"embodiment" might not be covered by any claims filed with this patent
document, but described as an "embodiment" to show the scope of the
invention and indicate that it might (or might not) covered in a later
arising claim (for example, an amended claim, a continuation application
claim, a divisional application claim, a reissue application claim, a
re-examination proceeding claim, an interference count); also, an
embodiment that is indeed covered by claims filed with this patent
document might cease to be covered by claim amendments made during
prosecution.

[0064] First, second, third, etc. ("ordinals"): Unless otherwise noted,
ordinals only serve to distinguish or identify (e.g., various members of
a group); the mere use of ordinals shall not be taken to necessarily
imply order (for example, time order, space order).

[0065] Electrically Connected: means either directly electrically
connected, or indirectly electrically connected, such that intervening
elements are present; in an indirect electrical connection, the
intervening elements may include inductors and/or transformers.

[0066] Receive/provide/send/input/output: unless otherwise explicitly
specified, these words should not be taken to imply: (i) any particular
degree of directness with respect to the relationship between their
objects and subjects; and/or (ii) absence of intermediate components,
actions and/or things interposed between their objects and subjects.

[0067] Port: any structure capable of communicating an electronic signal
between a coupler and a current carrier external to the coupler; some
ports may be as simple as the termination of a wire or trace; other ports
may be structured as printed circuit board pads or detachably attachable
connectors (for example, a sub-miniature type A connector).

[0068] Unless otherwise explicitly provided in the claim language, steps
in method steps or process claims need only be performed in the same time
order as the order the steps are recited in the claim only to the extent
that impossibility or extreme feasibility problems dictate that the
recited step order be used. This broad interpretation with respect to
step order is to be used regardless of whether the alternative time
ordering(s) of the claimed steps is particularly mentioned or discussed
in this document--in other words, any step order discussed in the above
specification shall be considered as required by a method claim only if
the step order is explicitly set forth in the words of the method claim
itself. Also, if some time ordering is explicitly set forth in a method
claim, the time ordering claim language shall not be taken as an implicit
limitation on whether claimed steps are immediately consecutive in time,
or as an implicit limitation against intervening steps.